Big differences in produce shelf life, study finds

Produce shelf life can vary widely between supermarkets and about half of the products sampled in a recent study spoiled prematurely, according to new research from Zest Labs.

Zest Labs said Monday that it examined random samples of strawberry clamshells, hearts of romaine lettuce and packaged salad mixes purchased from eight major U.S. grocery store chains between February and May. The study — titled “Half-Bad Is Not Good” — found that the freshness “varied significantly” from store to store and within individual stores, leading to early spoilage.

Of the items purchased, 58% of the strawberries, 54% of the packaged salad mixes and 49% of the romaine hearts spoiled before the expected shelf-life periods. San Jose, Calif.-based Zest Labs, a provider of freshness management solutions, said that consumers should “conservatively expect” to receive four days of shelf life for strawberries and packaged salad mixes and seven days for romaine hearts, based on academic studies and input from grocers.

“Most grocery stores assume that the produce they are receiving has uniform freshness or shelf life, but the data shows there is significant variation in freshness both between stores in a region and within the individual stores themselves,” Zest Labs CEO Peter Mehring said in a statement. “This shelf-life variability leads to dissatisfied customers who purchase produce that spoils before they can consume it and, as a result, may take their business elsewhere to find fresher, more consistent quality produce.”

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At individual stores, shelf life varied greatly — as much as 21 days for romaine hearts, 12 days for strawberries and nine days for packaged salad mixes, Zest Labs noted in its report. Several stores sold some produce that had expired or spoiled at the time of purchase, according to the study

“This inconsistent experience would mean, for example, a customer could buy a clamshell of strawberries on one shopping trip and it could last eight days and, on another trip, buy another clamshell to find it had already spoiled,” Zest Labs explained.

The sample base for the study included 10 stores for strawberries (with two stores from the same chain), nine stores for romaine lettuce (with two stores from the same chain) and five stores for packaged salad mixes.

“Zest Labs’ methodology for determining shelf life is based on years of university research on the effect of environmental conditions on the quality of fresh fruits and vegetables,” said Dr. Cecilia Nunes, Ph.D., associate professor at the University of South Florida, Department of Cell Biology, Microbiology and Molecular Biology. “Major universities including University of Florida and University of South Florida have confirmed that this approach is scientifically validated and accurate.”

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For consumers, produce freshness is critical in determining where they shop, and many consumers have had the experience of buying items that look good at the store but “go bad” at home shortly after purchase, Zest Labs pointed out. Its study cited Food Marketing Institute research finding that 80% of shoppers name high-quality fruit and vegetables as the most important attribute when selecting a primary store.

 “Certainly, growers, suppliers and grocers strive to sell the freshest produce but, due to variability in harvest conditions and post-harvest processing, the shelf life of fresh produce can vary significantly. Pallets of produce harvested in the same field on the same day can have dramatically different shelf lives due to harvest conditions, time spent in the field, cut-to-cool times, pre-cooling efficiency and effectiveness, and variations in shipping and handling,” Zest Labs said in the report. “This is also why ‘harvested on’ and ‘best by’ dates can be extremely misleading, as consumers may falsely expect produce to last to a certain date only to have it spoil earlier or toss it, thinking it has gone bad even if it is still actually fresh. Both situations lead to unnecessary waste.”

The research found no correlation between price and shelf life at the time of purchase. For the price factor, Zest Labs examined only strawberries because they have uniform packaging of one-pound clamshells.

Only a very limited sample size of the produce had a “best by” or “use by” date, according to the study. But in the six cases where a “use by” date was on the packaging, it was incorrect each time, “and often quite significantly,” Zest Labs said.

“The best way to prevent premature spoilage is to understand its cause,” the report concluded. “Zest Labs data shows that the primary causes of food waste occur in the first 24 to 48 hours after harvest, due to harvest conditions and post-harvest processing.”